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| United States Patent |
5,610,699
|
|
Yu
, et al.
|
March 11, 1997
|
Photoreceptor cleaning apparatus and method
Abstract
An apparatus for cleaning a charge retentive surface of a photoreceptor
which includes a cleaning blade for removing debris from the charge
retentive surface of a photoreceptor. In the environment of a xerographic
copier and/or printer, corona effluents are emitted by the high voltage
charging devices. These effluents, which are strong oxidizing agents, may
be adsorbed by or otherwise attach a cleaning blade polymer matrix.
Thereafter, such corona species outgassing from a blade may chemically
and/or otherwise attack the photoreceptor during prolonged
blade/photoreceptor contact, resulting in print/copy defects, as well as
permanent damage to the photoreceptor and/or cleaning blade. The present
invention relates to impregnating or otherwise treating the cleaning blade
with an antioxidant such that its presence in the blade polymer matrix can
prevent corona species penetration or accumulation by chemically
neutralizing and destroying the species upon exposure. In one example, the
cleaning blade is impregnated with an antioxidant such as
1,3-Diphenylisobenzofuran. Such preventive measures to hinder or eliminate
the corona species absorption and accumulation in the cleaning blade
polymer matrix can, in principle, be employed to resolve the corona
species outgassing problem.
| Inventors:
|
Yu; Robert C. U. (Webster, NY);
Schneider; Eric J. (Webster, NY)
|
| Assignee:
|
Xerox Corporation (Stamford, CT)
|
| Appl. No.:
|
274065 |
| Filed:
|
July 12, 1994 |
| Current U.S. Class: |
399/350; 15/256.5 |
| Intern'l Class: |
G03G 021/00 |
| Field of Search: |
355/299
430/490,125
15/256.5,256.51
428/408.8
|
References Cited
U.S. Patent Documents
| 4264191 | Apr., 1981 | Gerbasi et al.
| |
| 4563408 | Jan., 1986 | Lin et al. | 430/59.
|
| 4669144 | Jun., 1987 | Yasukawa et al. | 15/250.
|
| 4823161 | Apr., 1989 | Yamada et al. | 355/299.
|
| 4864331 | Sep., 1989 | Boyer et al. | 346/159.
|
| 4875081 | Oct., 1989 | Goffe et al. | 355/303.
|
| 5138395 | Aug., 1992 | Lindblad et al. | 355/299.
|
| 5153657 | Oct., 1992 | Yu et al. | 355/299.
|
| 5208639 | May., 1993 | Thayer et al. | 355/299.
|
| Foreign Patent Documents |
| 2-176690 | Jul., 1990 | JP.
| |
| 4-73677 | Mar., 1992 | JP.
| |
| 5-210338 | Aug., 1993 | JP.
| |
Primary Examiner: Ramirez; Nestor R.
Attorney, Agent or Firm: Webber; Don L.
Claims
We claim:
1. An apparatus for removing debris from a surface, comprising:
a cleaning blade including at least an end region contacting the surface to
remove debris therefrom; and
an antioxidant for neutralizing oxidizing agents present in the end region
of said cleaning blade, wherein said antioxidant comprises a material
selected from the group consisting of: 1,3-Diphenylisobenzofuran;
2-tert-Butyl-4-methyl phenol; 2-tert-Butyl-5-methyl phenol;
2-tert-Butyl-6-methyl phenol; 2,6-Di-tert-Butyl-4-methyl phenol;
1,4-Diamino naphthalene; Phenylene diamine; Alpha tecopherol;
N-Phenyl-2-naphthylamine; N-tert-Butyl-alpha-phenylnitrone.
2. The apparatus of claim 1, wherein said antioxidant is impregnated in the
end region of said cleaning blade body.
3. The apparatus of claim 1, wherein said antioxidant is applied to an
external surface of the end region of said cleaning blade.
4. The apparatus of claim 1, wherein said cleaning blade comprises a
polyurethane.
5. An apparatus for removing debris from a surface, comprising:
a cleaning blade including at least an end region contacting the surface to
remove debris therefrom; and
an antioxidant for neutralizing oxidizing agents present in the end region
of said cleaning blade, wherein said antioxidant is impregnated in an
amount, by percent weight of said cleaning blade, ranging from about
0.0001% to about 5% in the end region of said cleaning blade.
6. An apparatus for removing debris from a surface, comprising:
a cleaning blade including at least an end region contacting the surface to
remove debris therefrom; and
an antioxidant for neutralizing oxidizing agents present in the end region
of said cleaning blade, wherein said antioxidant is impregnated in an
amount, by percent weight of said cleaning blade, ranging from about
0.001% to about 2% in the end region of said cleaning blade.
7. An apparatus for removing debris from a surface, comprising:
a cleaning blade including at least an end region contacting the surface to
remove debris therefrom; and
an antioxidant for neutralizing oxidizing agents present in the end region
of said cleaning blade, wherein said antioxidant is impregnated in an
amount, by percent weight of said cleaning blade, of about 0.0028% in the
end region of said cleaning blade.
8. A printing machine of the type having an imaging receiving surface with
debris thereon, comprising:
a cleaning blade including at least an end region contacting the surface to
remove debris therefrom; and
an antioxidant for neutralizing oxidizing agents present in the end region
of said cleaning blade, wherein said antioxidant comprises a material
selected from the group consisting of: 1,3-Diphenylisobenzofuran;
2-tert-Butyl-4-methyl phenol; 2-tert-Butyl-5-methyl phenol;
2-tert-Butyl-6-methyl phenol; 2,6-Di-tert-Butyl-4-methyl phenol;
1,4-Diamino naphthalene; Phenylene diamine; Alpha tecopherol;
N-Phenyl-2-naphthylamine; N-tert-Butyl-alpha-phenylnitrone.
9. The printing machine of claim 8, wherein said antioxidant is impregnated
in the end region of said cleaning blade body.
10. The printing machine of claim 8, wherein said antioxidant is applied to
an external surface of the end region of said cleaning blade.
11. The printing machine of claim 8, wherein said cleaning blade comprises
a polyurethane.
12. A printing machine of of the type having an imaging receiving surface
with debris thereon, comprising:
a cleaning blade including at least an end region contacting the surface to
remove debris therefrom; and
an antioxidant for neutralizing oxidizing agents present in the end region
of said cleaning blade, wherein said antioxidant is impregnated in an
amount, by percent weight of said cleaning blade, ranging from about
0.0001% to about 5% in the end region of said cleaning blade.
13. A printing machine of the type having an imaging receiving surface with
debris thereon, comprising:
a cleaning blade including at least an end region contacting the surface to
remove debris therefrom; and
an antioxidant for neutralizing oxidizing agents present in the end region
of said cleaning blade, wherein said antioxidant is impregnated in an
amount, by percent weight of said cleaning blade, ranging from about
0.001% to about 2% in the end region of said cleaning blade.
14. A printing machine of the type having an imaging receiving surface with
debris thereon, comprising:
a cleaning blade including at least an end region contacting the surface to
remove debris therefrom; and
an antioxidant for neutralizing oxidizing agents present in the end region
of said cleaning blade, wherein said antioxidant is impregnated in an
amount, by percent weight of said cleaning blade, of about 0.0028% in the
end region of said cleaning blade.
15. A method for preparing a cleaning blade for removing debris from a
surface, comprising the step of:
treating the cleaning blade with an antioxidant for neutralizing oxidizing
agents present in at least an area where the cleaning blade body contacts
the surface, wherein said antioxidant comprises a material selected from
the group consisting of: 1,3-Diphenylisobenzofuran; 2-tert-Butyl-4-methyl
phenol; 2-tert-Butyl-5-methyl phenol; 2-tert-Butyl-6-methyl phenol;
2,6-Di-tert-Butyl-4-methyl phenol; 1,4-Diamino naphthalene; Phenylene
diamine; Alpha tecopherol; N-Phenyl-2-naphthylamine;
N-tert-Butyl-alpha-phenylnitrone.
16. The method of claim 15, wherein said treating step comprises the step
of impregnating the antioxidant in the cleaning blade.
17. The method of claim 15, wherein said treating step comprises the step
of applying a coating including the antioxidant to the cleaning blade.
18. A method for preparing a cleaning blade for removing debris from a
surface, comprising the step of:
treating the cleaning blade with an antioxidant for neutralizing oxidizing
agents present in at least an area where the cleaning blade body contacts
the surface by impregnating the antioxidant in the cleaning blade in an
amount, by percent weight of the cleaning blade, ranging from about
0.0001% to about 5%.
19. The method of claim 18, wherein said impregnating step comprises the
step of submersing the cleaning blade in a solution prepared by dissolving
0.041 grams of powdered 1,3-Diphenylisobenzofuran in 3,180 grams of
methylene chloride.
20. The method of claim 18, wherein said impregnating step comprises the
step of drying the cleaning blade.
21. The method of claim 20, wherein said impregnating step further
comprises partially drying the cleaning blade under vacuum.
22. A method for preparing a cleaning blade for removing debris from a
surface, comprising the step of:
treating the cleaning blade with an antioxidant for neutralizing oxidizing
agents present in at least an area where the cleaning blade body contacts
the surface by impregnating the antioxidant in the cleaning blade in an
amount, by percent weight of the cleaning blade, ranging from about 0.001%
to about 2%.
23. A method for preparing a cleaning blade for removing debris from a
surface, comprising the step of:
treating the cleaning blade with an antioxidant for neutralizing oxidizing
agents present in at least an area where the cleaning blade body contacts
the surface by impregnating the antioxidant in the cleaning blade in an
amount, by percent weight of the cleaning blade, of about 0.0028%.
Description
The present invention relates to a electronic reprographic image forming
apparatus, and more particularly to an improved cleaning device for
cleaning residual toner and other debris from a charge retentive belt or
drum surface of an image forming apparatus.
In electrophotographic applications such as xerography, a charge retentive
photoreceptor belt or drum is electrostatically charged according to the
image to be produced. In a digital printer, an input device such as a
raster output scanner controlled by an electronic subsystem can be adapted
to receive signals from a computer and to transpose these signals into
suitable signals so as to record an electrostatic latent image
corresponding to the document to be reproduced on the photoreceptor. In a
digital copier, an input device such as a raster input scanner controlled
by an electronic subsystem can be adapted to provide an electrostatic
latent image to the photoreceptor. In a light lens copier, the
photoreceptor may be exposed to a pattern of light or obtained from the
original image to be reproduced. In each case, the resulting pattern of
charged and discharged areas on photoreceptor form an electrostatic charge
pattern (an electrostatic latent image) conforming to the original image.
The electrostatic image on the photoreceptor may be developed by contacting
it with a finely divided electrostatically attractable toner. The toner is
held in position on the photoreceptor image areas by the electrostatic
charge on the surface. Thus, a toner image is produced in conformity with
a light image of the original beam reproduced. Once each toner image is
transferred to a substrate, and the image affixed thereto form a permanent
record of the image to be reproduced. In the case of multicolor copiers
and printers, the complexity of the image transfer process is compounded,
as four or more colors of toner may be transferred to each substrate
sheet. Once the single or multicolored toner is applied to the substrate,
it is permanently affixed to the substrate sheet by fusing so as to create
the single or multicolor copy or print.
Following the photoreceptor to substrate toner transfer process, it is
necessary to at least periodically clean the charge retentive surface of
the photoreceptor. In order to obtain the highest quality copy or print
image, it is generally desirable to clean the photoreceptor each time
toner is transferred to the substrate. In addition to removing excess or
residual toner, other particles such as paper fibers, toner additives and
other impurities (hereinafter collectively referred to as "residue") may
remain on the charged surface of the photoreceptor. Cleaning blades and
brushes may be employed to remove residue from a photoreceptor. An
elastomeric polyurethane blade may be used to scrape residue from the
photoreceptor surface. A rotating cleaning brush may remove, loosen,
dislodge, abrade or otherwise clean unwanted toner and other residue from
the photoreceptor.
The use of an elastomeric polyurethane blade to clean the residue toners
from the surface of an organic photoreceptor belt or drum at times
previously required the use of a mechanically assisted system to retract
the cleaning blade away from the photoreceptor surface when machine idled,
in order to prevent the blade from causing undesirable mechanical and/or
chemical effects to the photoreceptor. However, the implementation of
blade retraction mechanisms can add not insignificant costs and problems
in such machines.
To reduce cost of copier production using organic photoreceptor with a
blade cleaning system, it is desirable not to use a blade retraction
system, which can save costs and eliminate the service and repair
requirements associated with such a device. Unfortunately, eliminating
such a blade retraction system can lead to copy defect printout problems
that such systems are intended to prevent. The copy defect problems that
can occur include visible inboard-outboard transverse defect lines in
copies and prints corresponding to the location where the photoreceptor
and blade are in contact during machine is idling.
During xerographic imaging and cleaning processes, one can envision that
the elastomeric cleaning blade can absorb and cumulatively store a
substantial amount of corona species into the polymer matrix of the
cleaning blade. These corona species are emitted from high voltage
charging devices (such as corotrons and scorotrons). The corona species
absorbed by the cleaning blade can then outgas from the cleaning blade so
as to chemically attack the electrically active components in the
photoreceptor. This attack may be at the location where blade tip/edge and
photoreceptor make prolonged intimate contact, thus causing repetitive
(print defect) development of a narrow area of photoreceptor chemical
damage which manifests itself as a deletion band or a solid print/copy
line defect, depending on the development system employed in the copier or
printer. The damage to the photoreceptor can be long lived, and may
generally only be corrected by outright replacement of the photoreceptor
and cleaning blade. In some cases, the print defect may appear after only
a few thousand copies; in a machine having a photoreceptor life target of
far exceeding this output, such a premature failure represents a major
component life shortfall.
If the corona species chemically attack the photoreceptor during
blade/photoreceptor contact or proximity, preventive measures to lessen or
eliminate the corona species absorption and accumulation in the blade
polymer matrix can be employed to resolve the problem. Corona effluents
emitted by the high voltage charging device are strong oxidizing agents;
as such, the use of an antioxidant can provide the blade with an added
capability of being able to perform the functions of corona scavenging, by
neutralizing the corona species.
Various approaches have been employed to deal with problems associated with
photoreceptor cleaning and oxidation in copying or printing machine
environments, including the following disclosures that may be relevant:
U.S. Pat. No. 5,208,639 Patentee: Thayer et al. Issued: May 4, 1993
U.S. Pat. No. 5,153,657 Patentee: Yu et al. Issued: Oct. 6, 1992
U.S. Pat. No. 5,138,395 Patentee: Lindblad et al. Issued Aug. 11, 1992
U.S. Pat. No. 4,875,081 Patentee: Goffe et al. Issued: Oct. 17, 1989
U.S. Pat. No. 4,864,331 Patentee: Boyer et al. Issued: Sep. 5, 1989
U.S. Pat. No. 4,563,408 Patentee: Lin et al. Issued: Jan. 7, 1986
U.S. Pat. No. 4,264,191 Patentee: Gerbasi et al. Issued: Apr. 28, 1981
U.S. Pat. No. 5,208,639 to Thayer et al discloses an apparatus for cleaning
residual toner and debris from a moving charge retentive surface of an
image forming apparatus. The invention includes a multiple blade holder
for selectively indexing each individual blade into position for cleaning
the moving photoreceptor. The blade holder contains a number of cleaning
blades mounted radially from a central core; by rotating the holder about
its longitudinal axis a new cleaning blade is moved by the indexing device
into the cleaning position to replace a failed blade. The indexing device
removes the failed cleaning blade and positions a new cleaning blade in
frictional contact with the photoreceptor for cleaning.
U.S. Pat. No. 5,138,395 to Lindblad et al discloses a cleaning blade which
is made from a thermoplastic material having a compounded additive for
lubrication. The cleaning blade is used in an electrophotographic printing
machine to remove residual particles from a photoconductive surface.
U.S. Pat. No. 5,153,657 to Yu et al discloses a blade member impregnated
with inorganic particulates dispersed therein so as to reinforce the blade
for improving blade life.
U.S. Pat. No. 4,875,081 to Goffe et al discloses a blade member for
cleaning a photoreceptor wherein an A.C. voltage is applied to the
cleaning blade. Use of the A.C. voltage eliminates the need to bias the
blade against the photoreceptor with a high frictional force and thus
eliminates impaction of toner on the photoreceptor surface.
U.S. Pat. No. 4,864,331 to Boyer et al discloses an offset electrostatic
imaging process which includes the steps: (a) forming a latent
electrostatic image on a dielectric imaging member, with the dielectric
imaging member being prepared by coating an electrically conductive
substrate with a porous layer of a non-photoconductive metal oxide using a
deposition process; (b) developing the latent electrostatic image with a
developer material which comprises a silicone polymer and from about 0.5
to about 5 percent by weight of a metal salt of a fatty acid; (c)
transferring the developed image to an image receiving surface by applying
pressure between the dielectric imaging member and the image receiving
surface; (d) cleaning the dielectric imaging member using a first cleaning
means which is effective to remove developer material residue from about
the surface of the porous oxide layer; and (e) further cleaning the
dielectric imaging member using a second cleaning means which is effective
to remove developer material residue from the pores below the surface of
the oxide layer.
U.S. Pat. No. 4,563,408 to Lin et al. discloses an electrophotographic
imaging member, which includes a conductive layer, a charge transport
layer comprising an aromatic amine charge transport or hydrazone molecule
in a continuous polymeric binder phase, and a contiguous charge generation
layer comprising a photoconductive material, a polymeric binder and a
hydroxyaromatic antioxidant. An electrophotographic imaging process using
this member is also described.
U.S. Pat. No. 4,264,191 to Gerbasi et al. describes a laminated doctor
blade for removing excess marking material or other material from a
surface. The blade comprises a relatively hard layer of a smooth tough
material and a relatively soft layer of resilient material.
In accordance with one aspect of the present invention, there is provided
an apparatus for removing debris from a surface including a cleaning blade
including at least an end region contacting the surface to remove debris
therefrom and an antioxidant for neutralizing oxidizing agents present in
the end region of the cleaning blade.
In accordance with another aspect of the present invention, there is
provided a printing machine of the type having an imaging receiving
surface with debris thereon, including a cleaning blade including at least
an end region contacting the surface to remove debris therefrom and an
antioxidant for neutralizing oxidizing agents present in the end region of
the cleaning blade.
In accordance with another aspect of the present invention, there is
provided a method for preparing a cleaning blade for removing debris from
a surface, comprising the step of treating the cleaning blade with an
antioxidant for neutralizing oxidizing agents present in at least an area
where the cleaning blade body contacts the surface.
The invention will be described in detail with reference to the following
drawings, in which like reference numerals are used to refer to like
elements. The various aspects of the present invention will become
apparent as the following description proceeds and upon reference to the
drawings, in which:
FIG. 1 is a sectional, elevational view of the cleaning blade of the
present invention;
FIG. 2 is a diagram showing a chemical constituent of a crosslinked
polyurethane network structure of an exemplary photoreceptor cleaning
blade;
FIG. 3 is a diagram showing a molecular structure of an exemplary
antioxidant agent; and
FIG. 4 is a schematic elevational view showing an exemplary
electrophotographic printing machine which may incorporate the features of
the present invention therein.
While the present invention will hereinafter be described in connection
with preferred embodiments, it will be understood that it is not intended
to limit the invention to a particular embodiment. On the contrary, it is
intended to cover all alternatives, modifications and equivalents as may
be included within the spirit and scope of the invention as defined by the
appended claims.
For a general understanding of the features of the present invention,
reference is made to the drawings. In the drawings, like reference
numerals have been used throughout to designate like elements. It will
become evident from the following discussion that the present invention
and the various embodiments set forth herein are suited for use in a wide
variety of printing and copying systems, and are not necessarily limited
in its application to the particular systems shown herein.
To begin by way of general explanation, FIG. 4 is a schematic elevational
view showing an electrophotographic printing machine which may incorporate
features of the present invention therein. It will become evident from the
following discussion that the present invention is equally well suited for
use in a wide variety of copying and printing systems, and is not
necessarily limited in its application to the particular system shown
herein. As shown in FIG. 4, during operation of the printing system, a
multiple color original document 38 is positioned on a raster input
scanner (RIS), indicated generally by the reference numeral 10. The RIS
contains document illumination lamps, optics, a mechanical scanning drive,
and a charge coupled device (CCD array). The RIS captures the entire image
from original document 38 and converts it to a series of raster scan lines
and moreover measures a set of primary color densities, i.e. red, green
and blue densities, at each point of the original document. This
information is transmitted as electrical signals to an image processing
system (IPS), indicated generally by the reference numeral 12. IPS 12
converts the set of red, green and blue density signals to a set of
colorimetric coordinates.
The IPS contains control electronics which prepare and manage the image
data flow to a raster output scanner (ROS), indicated generally by the
reference numeral 16. A user interface (UI), indicated generally by the
reference numeral 14, is in communication with IPS 12. UI 14 enables an
operator to control the various operator adjustable functions. The
operator actuates the appropriate keys of UI 14 to adjust the parameters
of the copy. UI 14 may be a touch screen, or any other suitable control
panel, providing an operator interface with the system. The output signal
from UI 14 is transmitted to IPS 12. The IPS then transmits signals
corresponding to the desired image to ROS 16, which creates the output
copy image. ROS 16 includes a laser with rotating polygon mirror blocks.
Preferably, a nine facet polygon is used. The ROS illuminates, via mirror
37, the charged portion of a photoconductive belt 20 of a printer or
marking engine, indicated generally by the reference numeral 18, at a rate
of about 400 pixels per inch, to achieve a set of subtractive primary
latent images. The ROS will expose the photoconductive belt to record
three latent images which correspond to the signals transmitted from IPS
12. One latent image is developed with cyan developer material. Another
latent image is developed with magenta developer material and the third
latent image is developed with yellow developer material. These developed
images are transferred to a copy sheet in superimposed registration with
one another to form a multicolored image on the copy sheet. This
multicolored image is then fused to the copy sheet forming a color copy.
With continued reference to FIG. 4, printer or marking engine 18 is an
electrophotographic printing machine. Photoconductive belt 20 of marking
engine 18 is preferably made from a polychromatic photoconductive
material. The photoconductive belt moves in the direction of arrow 22 to
advance successive portions of the photoconductive surface sequentially
through the various processing stations disposed about the path of
movement thereof. Photoconductive belt 20 is entrained about transfer
rollers 24 and 26, tensioning roller 28, and drive roller 30. Drive roller
30 is rotated by a motor 32 coupled thereto by suitable means such as a
belt drive. As roller 30 rotates, it advances belt 20 in the direction of
arrow 22.
Initially, a portion of photoconductive belt 20 passes through a charging
station, indicated generally by the reference numeral 33. At charging
station 33, a corona generating device 34 charges photoconductive belt 20
to a relatively high, substantially uniform potential.
Next, the charged photoconductive surface is rotated to an exposure
station, indicated generally by the reference numeral 35. Exposure station
35 receives a modulated light beam corresponding to information derived by
RIS 10 having multicolored original document 38 positioned thereat. The
modulated light beam impinges on the surface of photoconductive belt 20.
The beam illuminates the charged portion of the photoconductive belt to
form an electrostatic latent image. The photoconductive belt is exposed
three times to record three latent images thereon.
After the electrostatic latent images have been recorded on photoconductive
belt 20, the belt advances such latent images to a development station,
indicated generally by the reference numeral 39. The development station
includes four individual developer units indicated by reference numerals
40, 42, 44 and 46. The developer units are of a type generally referred to
in the art as "magnetic brush development units." Typically, a magnetic
brush development system employs a magnetizable developer material
including magnetic carrier granules having toner particles adhering
triboelectrically thereto. The developer material is continually brought
through a directional flux field to form a brush of developer material.
The developer material is constantly moving so as to continually provide
the brush with fresh developer material. Development is achieved by
bringing the brush of developer material into contact with the
photoconductive surface. Developer units 40, 42, and 44, respectively,
apply toner particles of a specific color which corresponds to the
compliment of the specific color separated electrostatic latent image
recorded on the photoconductive surface.
The color of each of the toner particles is adapted to absorb light within
a preselected spectral region of the electromagnetic wave spectrum. For
example, an electrostatic latent image formed by discharging the portions
of charge on the photoconductive belt corresponding to the green regions
of the original document will record the red and blue portions as areas of
relatively high charge density on photoconductive belt 20, while the green
areas will be reduced to a voltage level ineffective for development. The
charged areas are then made visible by having developer unit 40 apply
green absorbing (magenta) toner particles onto the electrostatic latent
image recorded on photoconductive belt 20. Similarly, a blue separation is
developed by developer unit 42 with blue absorbing (yellow) toner
particles, while the red separation is developed by developer unit 44 with
red absorbing (cyan) toner particles. Developer unit 46 contains black
toner particles and may be used to develop the electrostatic latent image
formed from a black and white original document. Each of the developer
units is moved into and out of an operative position. In the operative
position, the magnetic brush is substantially adjacent the photoconductive
belt, while in the nonoperative position, the magnetic brush is spaced
therefrom. (In FIG. 4, each developer unit 40, 42, 44 and 46 is shown in
the operative position.) During development of each electrostatic latent
image, only one developer unit is in the operative position, with the
remaining developer units are in the nonoperative position. This insures
that each electrostatic latent image is developed with toner particles of
the appropriate color without commingling.
After development, the toner image is moved to a transfer station,
indicated generally by the reference numeral 65. Transfer station 65
includes a transfer zone, generally indicated by reference numeral 64. In
transfer zone 64, the toner image is transferred to a sheet of support
material, such as plain paper amongst others. At transfer station 65, a
sheet transport apparatus, indicated generally by the reference numeral
48, moves the sheet into contact with photoconductive belt 20. Sheet
transport 48 has a pair of spaced belts 54 entrained about a pair of
substantially cylindrical rollers 50 and 52. A sheet gripper (not shown in
FIG. 4) extends between belts 54 and moves in unison therewith. A sheet is
advanced from a stack of sheets 56 disposed on a tray. A friction retard
feeder 58 advances the uppermost sheet from stack 56 onto a pre-transfer
transport 60. Transport 60 advances a sheet (not shown in FIG. 3) to sheet
transport 48. The sheet is advanced by transport 60 in synchronism with
the movement of the sheet gripper. In this way, the leading edge of the
sheet arrives at a preselected position, i.e. a loading zone, to be
received by the open sheet gripper. The sheet gripper then closes securing
the sheet thereto for movement therewith in a recirculating path. The
leading edge of the sheet is secured releasably by the sheet gripper. As
belts 54 move in the direction of arrow 62, the sheet moves into contact
with the photoconductive belt, in synchronism with the toner image
developed thereon. In transfer zone 64, a gas directing mechanism (not
shown in FIG. 4) directs a flow of gas onto the sheet to urge the sheet
toward the developed toner image on photoconductive member 20 so as to
enhance contact between the sheet and the developed toner image in the
transfer zone. Further, in transfer zone 64, a corona generating device 66
charges the backside of the sheet to the proper magnitude and polarity for
attracting the toner image from photoconductive belt 20 thereto. The sheet
remains secured to the sheet gripper so as to move in a recirculating path
for three cycles. In this way, three different color toner images are
transferred to the sheet in superimposed registration with one another.
One skilled in the art will appreciate that the sheet may move in a
recirculating path for four cycles when under color black removal is used.
Each of the electrostatic latent images recorded on the photoconductive
surface is developed with the appropriately colored toner and transferred,
in superimposed registration with one another, to the sheet to form the
multicolor copy of the colored original document.
After the last transfer operation, the sheet transport system directs the
sheet to a vacuum conveyor 68. Vacuum conveyor 68 transports the sheet, in
the direction of arrow 70, to a fusing station, indicated generally by the
reference numeral 71, where the transferred toner image is permanently
fused to the sheet. The fusing station includes a heated fuser roll 74 and
a pressure roll 72. The sheet passes through the nip defined by fuser roll
74 and pressure roll 72. The toner image contacts fuser roll 74 so as to
be affixed to the sheet. Thereafter, the sheet is advanced by a pair of
rolls 76 to a catch tray 78 for subsequent removal therefrom by the
machine operator.
The final processing station in the direction of movement of belt 20, as
indicated by arrow 22, is a photoreceptor cleaning station, indicated
generally by the reference numeral 99, and as partially described in
greater detail in association with FIGS. 1 and 3. Cleaning blade 100 may
serve as the primary or backup means of toner and debris removal. Cleaning
blade 100 is shown proximate to corona generating device 34 (as well as
other environmental (electrical, mechanical and/or chemical) problem
sources such as are addressed by the cleaning blades of the present
invention. Other aspects and embodiments of the photoreceptor cleaning
blades of the present invention, such as those as shown and described in
association with FIGS. 1 and 3 and Examples II and III below, may be
employed in cleaning photoreceptors. A rotatably mounted fibrous brush 102
may be positioned in the cleaning station and maintained in contact with
photoconductive belt 20 to preclean and remove residual toner particles
remaining after the transfer operation. Thereafter, lamp 82 illuminates
photoconductive belt 20 to remove any residual charge remaining thereon
prior to the start of the next successive cycle.
FIG. 1 shows a photoreceptor cleaning blade 100 for removing residual toner
and other debris from the charge retentive surface of layer 21 (shown in
FIG. 1, on a flat portion of a belt photoreceptor 20). Cleaning blade 100
is supported adjacent to photoreceptor 20 by a mounting flange or member
(not shown). Photoreceptor cleaning blade 100 of the present invention
provides for the application of a desired uniformly dispersed pressure or
contact force for cleaning photoreceptor 20. Photoreceptor cleaning blade
100 may be coupled with an elastomeric cleaning brush 102 as shown in FIG.
4, for removing residual toner and other debris from charge retentive
layer 21. Cleaning brush 102 preferably includes a plurality of bristles,
which must necessarily be constructed from a material that is softer than
the charge retentive surface of photoreceptor 20 so to prevent scratching
or other damage to the charge retentive surface. Cleaning blade 100 and
cleaning brush 102 preferably extend across the width of photoreceptor 20,
so as to cooperatively remove excess matter/debris from layer 21. Cleaning
blade 100 is mounted to a supporting structure (not shown) so as to be
held in place as shown in FIG. 1.
Photoreceptors can comprise either a single layer or a multilayer belt
structure, such as shown in FIG. 1, or a drum structure (not shown). A
photoconductive layer (such as layer 21 of photoreceptor 20 in FIG. 1) may
be a homogeneous layer of a single material such as vitreous selenium or
may be a composite of layers containing a photoconductor. The commonly
used multilayered or composite structure contains at least a
photogeneration layer, a charge transport layer and a conductive
substrate. The photogeneration layer generally contains a photoconductive
pigment and a polymeric binder. The charge transport layer (e.g., hole
transport layer) contains a polymeric binder and charge transport
molecules (e.g., aromatic amines, hydrazone derivatives, etc.). These
organic, low ionization potential hole transport molecules as well as the
polymeric binders are very sensitive to oxidative conditions arising from
photochemical, electrochemical and other chemical reactions.
In copiers electronic printers, cleaning blades are frequently exposed to
difficult environmental conditions, to include light, charging devices
such as corotrons, dicorotrons, scorotrons and the like, electric fields,
oxygen, oxidants and moisture. Undesirable chemical oxidative species are
often formed during corona charging in xerographic imaging processes which
may react with key organic components in the charge transport layer or
photogeneration layer of the photoreceptors. These unwanted chemical
reactions can cause photoreceptor degradation, poor charge acceptance and
cyclic instability. Several types of reactive chemical species that are
likely to be formed in the operational environment of a copier or an
electronic printer include:
(a) Oxidants (e.g., peroxides, hydroperoxides, ozone, oxygen, selenium,
selenium oxide, selenium alloys, arsenic oxide, vanadium oxide, VOPs and
the like) may vary depending on the type of photoreceptor used.
(b) Both organic and inorganic radicals and diradicals (e.g., R, RO.sub.2 ;
O.sub.2 ; NO.sub.2 ; OH; and the like).
(c) Ionic species having positive (e.g., aromatic amine +) or negative
(e.g., 0-) charges.
(d) Both singlet oxygen states (i.e., .sup.1 0.sub.2 (Sigma+g) and .sup.1
0.sub.2 (.DELTA.g) can form through a sensitized photooxidation mechanism.
The foregoing chemical species can be generated from chemical,
electrochemical and photochemical reactions as well as from the corona
discharge in air by a charging device. The oxidative intermediates and
their products can degrade the photoreceptor, cleaning blades and other
components. If the cleaning blade in contact with photoreceptor degrades
as a result of chemical and photochemical reactions, the photoreceptor
becomes conductive (e.g., develops high dark decay) and exhibits
regionalized print defects, poor charge acceptance, aging and stability
deficiencies. Depending on the degree of damage, the photoreceptor
degradation can lead to poor image quality, cycle-up, and cycle-down
problems or even an inability of a copier or an electronic printer to
produce a print. Belt or drum photoreceptors, in which ions, particulates
and other harmful may fall from a charging device onto or near a cleaning
blade/photoreceptor interface, can present a particularly oxidizing
environment.
Referring to FIG. 1, printer/copier inboard-outboard line print defects
have been identified to be caused by corona species outgassing from the
cleaning blade to chemically attack the photoreceptor belt 20 (or a
photoreceptor drum, not shown) at the area where cleaning blade 100
remains in contact with charge retentive layer 21 photoreceptor 20 during
long period of time machine idling. This photoreceptor damage is
permanent, and will require that both the photoreceptor and cleaning blade
be replaced. Cleaning blade 100 includes a lower surface 110, an upper
surface 112 and a lead edge 114; the intersection point of the lower
surface 110 and lead edge 114 is the portion of the cleaning blade which
most vigorously contacts charge retentive layer 21 of photoreceptor 20. As
photoreceptor 20 moves in direction 22, residual toner and other excess
debris is removed from photoreceptor 20. Polyurethane blade body material
116 of cleaning blade 100 is treated with antioxidant material 118 (shown
in representative fashion in FIG. 1). The antioxidant(s), as more fully
described in Examples II and III below, prevent damage to cleaning blade
100 and photoreceptor 20. Cleaning blade 100 may be impregnated with,
manufactured to include, or otherwise treated with the antioxidant
material/agent to combat cleaning blade and/or photoreceptor damage caused
by the outgassing of corona species. Cyclic print testing results
(according to the Examples to follow) have shown that the cleaning blade
of the present invention can neutralize the damaging outgassing effects so
as to permit the cleaning blade to reach full photoreceptor life target
without the onset of print defects and/or photoreceptor damage.
The antioxidant(s) prevent corona species from outgassing from a cleaning
blade, by neutralizing those corona species. The antioxidant treated blade
thus prevents chemical, electrochemical or other corona species-related
attack on the photoreceptor during blade/photoreceptor contact. This
preventive measure to hinders or eliminate the corona species absorption
and accumulation in the blade polymer matrix. Since corona effluents
emitted by the high voltage charging device are strong oxidizing agents,
impregnating the cleaning blade polymer matrix with an antioxidant can
prevent corona species penetration or accumulation by chemically
neutralizing and/or destroying the species upon exposure. This elimination
of the root cause of corona species outgassing from the blade, and the
print defect and cleaning blade/photoreceptor problems related thereto,
may be resolved by adopting the present invention, as described more
specifically in the following Examples:
EXAMPLE I
Untreated Cleaning Blade
An elastomeric polyurethane cleaning blade was prepared by reacting liquid
components of a prepolymer polyol (HOOH) with a diisocyanate crosslinker
(O.dbd.C.dbd.N--R--N.dbd.C.dbd.O, where R is an aliphatic or aromatic
functional) to form a crosslinked three-dimensional network elastomer. The
crosslinking reaction, upon mixing the two liquid components, leads to the
formation of a thermoset polyurethane elastomer, generally described as
shown in FIG. 2.
EXAMPLE II
An elastomeric polyurethane cleaning blade was prepared in the same manner
according to Example I, and was then impregnated with
1,3-Diphenylisobenzofuran. The presence of 1,3-Diphenylisobenzofuran in
the cleaning blade material matrix imparted to the blade a capability of
scavenging and neutralizing absorbed oxidizing agents of corona species
emitted from any charging device(s) during photoelectrical imaging and
cleaning processes, thus eliminating the corona species photoreceptor
attack problem altogether. To achieve this purpose, a polyurethane blade
weighing 12.3132 gms was submersed in a 0.00128 weight percent of
1,3-Diphenylisobenzofuran/methylene chloride solution (prepared by
dissolving 0.041 gm of 1,3-Diphenylisobenzofuran in 3,180 gms of methylene
chloride), and permitted to absorb the solution. The antioxidant used,
1,3-Diphenylisobenzofuran, was a finely divided yellowish powder and
having the unique molecular structure shown in FIG. 3, and was obtained
from Spectrum Chemical Manufacturing Corporation, a division of Janssen
Chimica.
When the polyurethane blade was placed in contact with the
thermodynamically good solvent methylene chloride, it would continuously
absorb the solvent, as well as the dissolved antioxidant, until the
increase in elastic free energy due to the three dimensional isotropic
expansion of the polyurethane network was offset by (balanced with) the
decrease in free energy due to mixing of polymer chain and this solvent
such that the condition of swelling equilibrium was reached. At this
swelling equilibrium state, the swollen polyurethane blade (at 39.2101
gms) was removed from the solution and then allowed to deswell and dry at
room ambient for at least 10 hours. The polyurethane blade was further
dried under vacuum for 3 hours to remove trace amounts of methylene
chloride. In that the antioxidant was nonvolatile, it thus remained
permanently in the material matrix of the blade. The total amount (by
weight percent) of antioxidant impregnated in the blade after the
swelling/deswelling process was determined, by multiplying the weight
percent of antioxidant concentration in solution by the total amount
(weight) of solution absorbed into the blade at swelling equilibrium state
and then dividing that by the weight of the original dry blade, as
follows:
##EQU1##
To achieve satisfactory antioxidant impregnation results according to
Example II, the loading of antioxidant in the cleaning blade should be
within the range of about 0.0001 weight percent to about 5 weight percent.
(A loading level below 0.0001 weight percent will diminish the
effectiveness of the antioxidant, while a level greater than 5 weight
percent may alter the mechanical properties of the blade.) A preferred
loading level ranges from about 0.001 weight percent to about 2 weight
percent, while, as discussed in Example II above, an optimum level should
be from about 0.002 weight percent to about 1 weight percent.
Although the exemplary experimental demonstrations outlined above focus on
1,3-Diphenylisobenzofuran, other antioxidants may also or alternatively
employed, such as, for example: 2-tert-Butyl-4-methyl phenol;
2-tert-Butyl-5-methyl phenol; 2-tert-Butyl-6-methyl phenol;
2,6-Di-tert-Butyl-4-methyl phenol; 1,4-Diamino naphthalene; Phenylene
diamine; Alpha tecopherol; N-Phenyl-2-naphthylamine;
N-tert-Butyl-alpha-phenylnitrone; and/or others. While impregnation of the
cleaning blade is described above as being completed after production of
the blade (Example I), similar results may likewise be obtained by
including antioxidants in the blade as part of the initial
manufacturing/fabrication process according to other methods.
EXAMPLE III
An elastomeric polyurethane cleaning blade was prepared in the same manner
according to Example I; the surfaces of the blade were thereafter treated
with a solution of a typical DAG (Dispersed Active Graphite) coating and
allowed to dry in lab ambient conditions. (The DAG coating was expected to
perform the same function as the antioxidant in Example II.) In
alternative embodiments, a surface impregnation, paint, dip, coat, or
other treatment including activated carbon, a polymer soluble in methylene
chloride (such as Makrolon or PE100) with a suitable % weight of
1,3-Diphenylisobenzofuran in solution might be used as a surface
treatment; antioxidants such as described in Example II above might also
be used in as a surface coating in lieu of or in addition to activated
carbon.
EXAMPLE IV
The polyurethane cleaning blade of Examples I and II were each tested in
extended duration trials in a xerographic printer/copier. The standard
testing procedures included a total daily copy volume of 800 to 1000
copies per day. At the beginning and end of each day a 30% solid area
coverage halftone pattern was made to observe the condition of the
photoreceptor with respect to cleaning blade lines. The test environment
was lab ambient and allowed to fluctuate through a normal office daily
cycle of approximately 68.degree. F./40% RH to approximately 75.degree.
F./50% RH. The untreated blade of Example I was again seen to cause the
development of a band of print defect in copies corresponding to the
location where blade make idle contact after only 2,000 prints. By
contrast, the antioxidant impregnated blade of Example II showed no
noticeable print defects after reaching an exemplary photoreceptor target
life of 18,000 prints, thus demonstrating the total effectiveness of the
present invention approach to eliminate the problem. Importantly, the
presence of antioxidant in the blade did not affect the blade cleaning
efficiency, and specifically, did not change the modulus, hardness, or
dynamic mechanical properties of the blade.
The polyurethane cleaning blade having the DAG surface treatment (described
in Example III) was also tested in a xerographic printer/copier, according
to the standard testing procedures set forth above. After 5000 prints, the
copy quality samples exhibited significantly reduced cleaning
blade-related print defects, although detectable print defect lines had
developed during testing. The presence of the print defect lines was
attributed to a wearout/wear through of the DAG coating at the cleaning
blade-to-photoreceptor interface.
In recapitulation, various embodiments of a drum or belt photoreceptor
cleaning system employing an antioxidant impregnated/treated cleaning
blade which permits the removal of residual toner and debris from the
charge retentive surface of a photoreceptor has been described.
While the present invention has been illustrated and described in detail in
the drawings and foregoing description, the same is to be considered as
illustrative and not restrictive in character, it being understood that
only the preferred embodiments have been shown and described and that all
changes and modifications that come within the spirit of the invention are
desired to be protected.
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